Spring-driven printing hammer arrangement

ABSTRACT

A printing hammer arrangement in which the hammer is under the action of a spring which can be locked and unlocked, in which a rotatable coupling pawl which is provided with an extra mass is arranged between the hammer and the spring. In the case of a swingable hammer the spring is a helical spring which engages a frame which is rigidly secured to the hammer. In laterally guided hammers, the spring is a leaf-spring which engages a pall pawl which is journalled on the hammer.

1 States Patent [1 1 Apr. 16, 1974 1 SPRING-DRIVEN PRINTING HAMMER ARRANGEMENT [75] Inventor: Peter Blume, Norderstedt, Germany [73] Assignee: U.S. Philips Corporation, New

York, NY.

[22] Filed: Nov. 28, 1972 [21] Appl. No.: 310,174

[30] Foreign Application Priority Data Dec. 3, 1971 Germany 2160032 1 [52] U.S. Cl .4 101/93 C [51] Int. Cl 1341,] 9/30 [58] Field of Search 101/93 C, 93 R, 287

[5 6] References Cited UNITED STATES PATENTS 3,587,456 1/1969 .laensch 101/93 C 3,507,214 4/1970 Anderson 101/93 C 3,164,085 I/l965 Hawkins 101/93 C 3,351,007 11/1967 Poland l0l/93 C 3/1972 Aegerinos et a1. l0l/93 C 7/1972 Huber et a1. l0l/93 C OTHER PUBLICATIONS IBM Technical Disclosure Bulletin, Vol. 5, No. 11, April 1963, pp. 27-29, Bear and McGuine.

Primary ExaminerRobert E. Pulfrey Assistant ExaminerE. M. Coven Attorney, Agent, or Firm-Frank R. Trifari ABSTRACT In the case of a swingable hammer the spring is a helical spring which engages a frame which is rigidly secured to the hammer. In laterally guided hammers, the spring is a leaf-spring which engages a pal] pawl which is journalled on the hammer.

4 Claims, 3 Drawing Figures PATENTEDAPR 16 I974 3.8041009 sum 1 BF 2 EQW SPRING-DRIVEN PRINTIING HAMMER ARRANGEMENT The invention relates to a printing hammer arrangement for printing on the fly, for example, for parallel printers, in which the hammer is influenced by a spring which can be locked and unlocked.

A number of printing hammer arrangements are already known in which the driving of the hammers occurs electromagnetically or electrodynamically. In said arrangements, the use of electro-mechanical converters has proven to be disadvantageous; due to their very poor efficiency to percent), and their comparatively large consumption of electric energies necessary for printing. Since up to I36 printing hammer units are arranged beside each other in the parallel printer, the heat dissipation in itself is a particular problem.

A much more favorable situation with respect to the electric energy consumption is obtained when servo drives are used. In these systems, the only function of the electromechanical converter is to start the driving process, while the energy itself is supplied by a mechanical energy buffer, forexample, from a container having compressed air in the case of pneumatic drives, or from a continuously rotating wheel in the case of impact wheel drives.

In the category of servo drives there also belong drives in which the energy is supplied by a tensioned spring. In the known spring drives, spring and hammer are often directly connected together. Because the spring is relaxed after printing in these systems, the hammer cannot return to its rest position. After impact, auxiliary measures are necessary to maintain the hammer in a position which is sufficiently far remote from the paper and the ink ribbon. In a known device, this is realized in that the hammer is clamped in a clamping device during its return stroke.

In another device, the energy present in the hammer during the return stroke is dissipated by the impact against a second movable mass, so that the system comes to rest in the neutral position of the spring. A drawback in these known devices is that their reliability depends upon relatively undefined properties, for example, the coefficient of friction of the clamping device, or the impact upon contacting a second mass. Furthermore, it is unfavorable for the hammer not to be returned to the starting position after impact. The hammer is usually considerably closer to the paper and the ink ribbon than is desirable.

These drawbacks can be avoided when the hammer, after the acceleration, is uncoupled from the spring. In some known constructions, this is achieved by a corresponding movement behavior of the spring and a resilient pawl. Due to the very rapid movement of the hammer and the very small free stroke, however, only little time is available to uncouple the spring and the pawl. An additional drawback is that uncoupling begins at zero velocity and hence, is extremely inert.

According to the invention, these drawbacks are avoided in that a rotatable coupling pawl which comprises an extra mass is provided between the hammer and the spring.

The coupling pawl is weighted by means of an extra mass. After the impact of the body (hammer or driving lever) which supports the pawl, it is rotated out of the engagement zone at a sudden initial angular velocity due to the inertia action of said extra mass. The velocity in the pawl-mass" system at the instant of uncoupling can without objection be made approximately as large as the velocity of the hammer. Therefore it is only necessary for the hammer to have a free stroke which is comparable to the distance over which uncoupling takes place.

The invention will be described in greater detail with reference to the drawing in which FIG. 1 is a schematic drawing of a rotational hammer mechanism according to the invention;

FIG. 2 is a schematic drawing of a translational hammer-mechanism according to the invention;

FIG. 3 is a graphical representation of the pawl showing the inertia effect.

In the device shown in FIG. 1, the hammer l, which is rotatably journalled about the pivot M, is maintained in the rest position by the action of the permanent magnet 2. By the tensioned helical spring 3, a force is exerted on the hammer via a driving lever 4, which is rigidly secured to the hammer 1 and the pawl 5. The spring force tries to move the hammer in the direction of the paper 6, the ink ribbon 7 and the type roller 8. At the time of printing, the action of the permanent magnetic field is removed for a short period of time, by

conveying a current through a coil which is secured to the limb 9 of the magnet. The hammer then moves under the influence of the spring resilience. After the hammer has covered a certain distance, and has the movement energy necessary for printing, the driving lever 4 which is connected to the spring 3, impacts against an abutment 10. As a result of its mass inertia, however, the hammer moves further forward. The mass 11 connected rigidly to the pawl 5 also continues to move. After the hammer has impacted the paper and the ink ribbon against the desired type, it is moved back to the rest position with a velocity which corresponds approximately to one third of the impact speed. The movement is supportedby a small spring 12. During the free stroke of the hammer, the pawl 5 is rotated'out of the field of the hammer by the inertia movement of the mass 11, so that the hammer can immediately return to the rest position without being hindered by the driving lever. It is held in the rest position by the permanent magnet. Since the rest position is approximately 3 mm remote from the point of impact, a double print resulting from impact vibrations is avoid'edwith certainty.

After the line to be printed has been fully printedby the parallel' arranged hammers, andthe set of types has once passed the printing place, respectively, the driving lever 4 is moved'back to the rest position by the pin 13 of the continuously rotating eccentric 14. The spring is tensioned, and the pawl 5 is coupled to the hammer by means of the spring 15. The printing cycle is thus completed, and the printing device is ready for printing the next line.

The printing device shown in FIG. 2 is of a construction similar to that of the above-described device of FIG. 1, and its pawl functions in like manner. However, instead'of the rotatably journalled hammer, a hammer 16 which is secured to the leaf springs 17 and 18 is provided, and a leaf spring l9is usedas a driving element. Since the pawl 20 weighted with the extra mass 21, is secured to the hammer, rotation of the pawl begins only when the hammer impacts, and not when the spring impacts the abutment 22. It can be proved, however, that for similar changes of linear velocity and pawl dimensions, the coupling pawl will pivot an equal distance to that obtained with a rotational hammer and lever.

FIG. 3 serves to illustrate the movement of the pawl. It is assumed that the pawl moves parallel to the X-axis at a velocity v, and is held in the point at the instant t= O (sudden fixing). As is derived, for example, in LS- zabo, Einfuhrung in die technische Mechanik, 7" edition, pp. 473 et seq., the pawl after fixing, performs a rotary movement about the fulcrum 0" at an angular velocity to. For the angular velocity the following equation is obtained:

(9 et/ 0 s in which y is the gravity distance in the Y direction, m is the total mass and 0 is the inertia moment about the fulcrum O. The tip of the pawl then has a velocity a M M 0 8 in which a is the distance from the tip of the pawl to the fulcrum.

By a suitable distribution of the masses over the arm and the head of the pawl, v,, can be made as large as v, to an approximation. In order to limit the energy losses of the system, the mass of the pawl must be kept minimum and the kinetic energy stored in the head of the pawl may not be more than 10 to percent of the overall energy.

With respect to the construction according to the invention, it is to be noted that the devices shown in FIGS. 1 and 2 are mere examples. It will be obvious that the system in FIG. 1 can be driven with a leaf spring, and the system shown in FIG. 2 can be driven with a helical spring. It is also possible to cause the permanent magnet to hold the driving lever 4 instead of the hammer. Finally, instead of the axial bearing for the lever and pawl, a leaf spring bearing without friction may be chosen.

What is claimed is:

I. A printing hammer arrangement for use in impact printers, comprising:

a printing hammer;

mounting means connected to said hammer for permitting movement of said hammer between a rest position and a printing position;

means for holding said hammer in said rest position and for releasing said hammer from said rest position;

a driving spring for accelerating said hammer from said rest position toward said printing position;

coupling means pivotably connected to said hammer for transmitting driving force from said spring to said hammer, said coupling means comprising a pawl having a weighted portion at one end thereof, the inertia of said weighted portion causing rotation of said pawl from a coupled position to an uncoupled position after said hammer has reached a pre-determined position while traveling from said rest position toward said printing position; and

means for re-setting said pawl after said hammer has returned to said rest position.

2. The printing hammer arrangement of claim 1 wherein said coupling means further comprises a driving lever pivotably connected at one end thereofto said hammer, said spring being connected to said lever at a point removed from said one end, said pawl being pivotably connected about a mid-portion thereof to said lever at a point removed from said one end, said pawl engaging said hammer at the end opposite said weighted portion when in said coupled position for transmitting driving force from said spring, and

said arrangement further comprises abutment means fixed in position for contacting said lever at a point removed from said one end when said hammer has reached said pre-determined position so as to stop motion of that portion of the lever, whereby the inertia of said weighted portion will rotate said pawl to said uncoupled position disengaging said pawl from said hammer.

3. The printing hammer arrangement of claim 2 wherein the hammer mounting means comprises a mounting for rotational movement of said hammer between said rest and printing positions about the same point at which said lever is connected to said hammer, and

said re-setting means comprises means for moving said lever out of contact with said abutment means.

tion. 

1. A printing hammer arrangement for use in impact printers, comprising: a printing hammer; mounting means connected to said hammer for permitting movement of said hammer between a rest position and a printing position; means for holding said hammer in said rest position and for releasing said hammer from said rest position; a driving spring for accelerating said hammer from said rest position toward said printing position; coupling means pivotably connected to said hammer for transmitting driving force from said spring to said hammer, said coupling means comprising a pawl having a weighted portion at one end thereof, the inertia of said weighted portion causing rotation of said pawl from a coupled position to an uncoupled position after said hammer has reached a predetermined position while traveling from said rest position toward said printing position; and means for re-setting said pawl after said hammer has returned to said rest position.
 2. The printing hammer arrangement of claim 1 wherein said coupling means further comprises a driving lever pivotably connected at one end thereof to said hammer, said spring being connected to said lever at a point removed from said one end, said pawl being pivotably connected about a mid-portion thereof to said lever at a point removed from said one end, said pawl engaging said hammer at the end opposite said weighted portion when in said coupled position for transmitting driving force from said spring, and said arrangement further comprises abutment means fixed in position for contacting said lever at a point removed from said one end when said hammer has reached said pre-determined position so as to stop motion of that portion of the lever, whereby the inertia of said weighted portion will rotate said pawl to said uncoupled position disengaging said pawl from said hammer.
 3. The printing hammer arrangement of claim 2 wherein the hammer mounting means comprises a mounting for rotational movement of said hammer between said rEst and printing positions about the same point at which said lever is connected to said hammer, and said re-setting means comprises means for moving said lever out of contact with said abutment means.
 4. A printing hammer arrangement according to claim 1, wherein said pawl is pivotably mounted about the mid-portion thereof to said hammer, engageable with said hammer at the weighted end thereof when in said coupled position, said driving spring engaging the opposite end of said pawl, said opposite end being out of engagement with said spring in said uncoupled position. 